Micromechanical Study of Rock Fracture and Fragmentation under Dynamic Loads using Discrete Element Method

摘要: The study presented in this thesis aims to numerically explore the micro-mechanisms underlying rock fracture and fragmentation under dynamic loading. approach adopted is based on Discrete Element Method (DEM) coupled Cohesive Process Zone (CPZ) theory. It assumes material as assemblage of irregular-sized deformable fragments joining together at their cohesive boundaries. simulation, which referred Fragment Model (CFM), takes advantage DEM particle/contact logic handle boundaries between. In idealization, mechanical properties particle more dominantly those contact control macroscopic response assemblage. A rate-dependent orthotropic law developed for contacts capture specific features, e.g. brittleness, anisotropy rate-dependency. Rock experimental behavior then modeled order assess individually sensitivity results grain size, confining pressure, micromechanical parameters, stored strain energy, loading rate etc. organized problem systematically. First, CFM application static analysis examined. shown that quantitatively qualitatively predicts compressive tensile failure hard soft rocks well shear strength, dilatancy degradation rough joints. micro-parameters, i.e., stiffness stiffness, friction are calibrated using a combination statistical disciplines original closed-form expressions. calibration process provides useful physical interpretation each micro-parameter terms standard properties. These interpretations enable understand how originates from its mineral microstructure. Energy needed fully open contact, energy represents CFM. Experimental investigations suggest independent quasi-static circumstances. Thus, simply assumed constant analysis. However, simulation fast fracturing by warns assumption causes serious deviations Laboratory observations reveal fast-moving consumes than slow-moving one does. This inspires consider variable provide model with appropriate prediction release process. Applying new approach, PMMA plates investigated different levels energy. As final stage, toughness samples, measured split-Hopkinson pressure bar test, simulated promising obtained. They demonstrate numerical modeling can practically aid methods measurement verification, error estimation, performing corrections. studies an effective convenient tool investigate problems. While predictions continuum models restricted only crack initiation, made it possible track both initiation progression over time following consecutive damage contacts. Moreover, research specifically demonstrates proposed properly result verifies validity adequacy